Louvered window coverings, such as venetian blinds, vertical blinds, shutters and other types of movable shades (generally referred to as "blinds"), are generally thought of as primarily providing privacy. However, significant heat is generated in enclosures by incident sunlight coming through windows. Because they regulate the amount of incident light within an enclosure, blinds thus play an important role in controlling the ambient temperature in the enclosure, and in conservation and efficient utilization of energy.
Most people prefer that the interior temperature of their homes remain at approximately 72 degrees Fahrenheit for optimal comfort. During the summer, for example, blinds may be closed to reduce heat and to save energy required for air conditioning to cool the air heated by light coming through the windows. During the winter, to take advantage of the heat generated by the light blinds may be opened during the day and closed at night to slow the loss of heat through the windows, thereby saving energy. As a significant amount of energy is consumed in heating and cooling enclosures, proper operation of blinds during the course of the seasons can materially contribute to energy conservation by its efficient utilization.
Blinds enhance security as well. When used on business premises, for example, blinds should be left open at night so that security personnel can peer through the windows. At home, however, the blinds should be closed.
Commercially available louvered window coverings are, with few exceptions, manually operated. Designers and manufactures know that successful blinds and shades should be of simple design for low cost, reliable operation and convenience of use, and simple designs are manually operated. To take full advantage of the benefits of movable or adjustable louvered window coverings, therefore, requires a vigilant person to operate the blinds, one who understands these benefits. As such circumstances are rare, so too are blinds rarely used to their fullest benefit and advantage. Blinds which automatically open and close are therefore desirable.
Despite the needs and desires for automatic systems, the industry still strongly favors the simple design of manual blinds. There have been attempts to automate operation of blinds, primarily for convenience of remote operation, though also to respond to changes in the environment, particularly the amount of light incident on the blinds. Previous attempts at automation have generally been, however, too costly and failed in terms of cost, reliability and adaptability to the wide variety of blind mechanisms.
The automation of blinds in the prior art has involved coupling the blind's positioning mechanism, typically a rod running the length of the blind that intercouples the slats of the blind for rotation in unison, to direct current (DC) motors or solenoids that generate the work necessary for opening and closing the blinds. They are also very noisy, making them less appealable. The motors hum, the solenoid actuator clicks, and the gears grind. Furthermore, DC motors and solenoids are relatively large and cumbersome. They often are not adaptable to some types of blind mechanisms. They also sometimes cannot be incorporated into the blind mechanism, but must be mounted either on a wall to pull a draw string, or to the outside of the housing for the blind mechanism. The latter case requires quite complex mechanical interfaces with the blind mechanisms, necessitating substantial and numerous types of modifications to the various types of preexisting blinds for retrofit, or special manufacture of blinds with the motors. Either way, simplicity is sacrificed and cost substantially increased.
The fact that DC motors and solenoids require a source of power for operation further increases cost and complexity. Each blind must be equipped with an AC to DC converter if power is taken from a wall socket. Otherwise, batteries must be used. Typically, they are expensive varieties, such as NiCad batteries, so that they do not have to be frequently replaced and may be recharged by expensive solar, photoelectric cells or circuitry to provide a constant trickle charge of current.
Moreover, to control the DC motors and solenoids during operation of the blind mechanism, relatively complex and expensive circuits must be used. These circuits are further complicated where the same circuit centrally controls several different types of blind mechanisms, as each mechanism potentially requires specialized operation of the DC motor or solenoids.